An American woman transformed her body in order to be healthy enough to donate a kidney to a former colleague living with chronic liver disease.

Rebekah Ceidro from Pittsburgh, Pennsylvania was saddened to read about her friend Chris Moore's plight on Facebook and began to investigate whether or not she might be a viable match to donate a kidney to him.

The pair were thrilled to discover they were indeed a blood type match, but unfortunately at more than 15st (95kg), Rebekah was told that she was too heavy to undergo surgery safely and would need to consider losing weight if she wished to continue.

Speaking to Today.com, Rebekah said it was tough to hear surgeons at the University of Pittsburgh Medical Centre tell her weight was an issue, but soon realised that they had her best interest at heart.

"Admittedly, I was really angry that two individual surgeons would have the audacity to say such a thing, but they were right,” Ceidro told the publication.

"My actual thought was, 'I’m too fat to save my friend’s life.' And that sucked, but that’s at least something you can change."

However, determined Rebekah (30) decided to embark on a fitness routine, and began to train for a local 5KM race.

"I thought, ‘This is what I’m going to do, I’m going to start running and keep running until I can do a 5K every day," she said.

Within six months, Rebekah was running up to 4km each day, and has shed a total of 3st (19kg) since beginning her fitness routine. The mum-of-one has now been approved by doctors to undergo organ donation surgery within the next three to six months.

Rebekah's friend Chris Moore expressed his gratitude towards his generous friend, and said she inspired him every day with her determination.

"I use her courage to give myself courage. If she can do this, then I can do this," Moore said.